1. Field of the Invention
The present invention relates to a compatible optical disk player and recording and/or reproducing method thereof, and more particularly, to a compatible optical disk player and recording and/or reproducing method using a single optical pickup for recording and/or reproducing data from different types of optical disks.
2. Description of the Related Art
Generally, an optical disk player records and/or reproduces data from an optical disk, such as an un-recordable or recordable compact disk (i.e., CD or CD-R), or a digital video disk (DVD). FIG. 1 is a schematic diagram illustrating a conventional optical pickup system for recording and/or reproducing data from a single optical disk.
As illustrated in FIG. 1, a light beam is emitted from a laser diode 1 and is split into three rays by a diffraction grating 2 used as a tracking servo. After passing through the diffraction grating 2, the beam is transmitted or reflected via a beam splitter 3. The beam splitter 3 has a coated layer 3a formed on a diagonal surface therein by which the beam is semi-transmitted or semi-reflected. The coated layer 3a may include a polarization coating layer on the diagonal surface for transmitting or reflecting the beam according to the type of the light polarization.
The beam splitter 3 transmits the beams from the diffraction grating 2. The three rays are then reflected by the coating layer 3a formed on the diagonal surface, and are concentrated by a collimator lens 4 in the form of a parallel ray. The parallel ray is then focused on the recording surface of the optical disk D via an objective lens 5.
After being focused on the recording surface of the optical disk D, the beam is reflected therefrom and passes through the objective lens 5, the collimator lens 4, and the beam splitter 3, sequentially. An astigmatism lens 7 converges the beam passed through the beam splitter 3 to the photo-detector 8. The photo-detector 8 detects the beam, which is used as a data signal for reproducing and a signal for tracking and focusing control.
However, the conventional optical pickup system described above can be used to record or reproduce data on or from only one type of optical disk. Further, in order to record or reproduce the data, the wavelength of the laser diode must vary depending on the density of the optical disk. Although the general arrangement of the conventional optical pickup system may be used to record or reproduce the data from various types of optical disks, different optical pickups, recording, and reproducing drives are required to record or reproduce the data on or from different optical disks, and thereby the system becomes costly and cumbersome.
For example, the disk drive for the CD or the CD-R needs a laser diode for emitting a laser beam of 780 nm wavelength. In contrast, the disk drive for the DVD, which has higher recording density than the CD or the CD-R, needs a laser diode for emitting a laser beam of 650 nm wavelength. Accordingly, different recording and/or reproducing drives need to be used to record or reproduce the data on or from different types of disks.
Many studies have been conducted to create a compatible recording and/or reproducing drive which can drive CD, CD-R, and DVD disks using a single optical pickup. An example of a compatible optical pickup employs a laser beam source having a single chip in which laser diodes for emitting laser beams of 780 nm and 650 nm wavelengths are built at a close distance to each other in order to reduce the number of components, such as the beam splitter. Specifically, the laser diodes are spaced at a predetermined distance from each other, such as 100–110 m. However, the distance between the laser diodes may create focus and tracking errors when arranging the optical pickup to emit the laser beam of 780 nm wavelength by straying the beam having 650 nm wavelength from an optical axis.
To compensate for these errors, typically a hologram is used to shift the directions of the beams to different places according to the wavelengths of the respective laser beams in a manner such that the beams are received by corresponding photo-detectors. Another embodiment uses a birefringence prism on the front surface of the photo-detector 8 to refract the laser beam for a DVD, which is strayed from the optical axis, to a proper location on the photo-detector 8. These embodiments, however, are costly, due to the additional optical components required such as the birefringence prism and the hologram. Further, because of the increased number of components, the installation of the prism and the hologram becomes complicated.